1. Field of the Invention
The present invention relates to an optical information reading device that reads information recorded in a recording medium by a hologram or the like.
2. Description of the Related Art
With prepaid cards, credit cards, debit cards and identification cards, it is necessary to determine whether or not the cards have been illegally forged or altered. As one method of determining this, a hologram is recorded on a credit card or bank card, and the hologram is read. With respect to gift cards also, holograms where characters, numbers or pictures change depending on the angle at which the card is viewed are disposed as a measure to prevent forgery. These holograms are promising as large-capacity, high-speed transferable recording media.
For example, as shown in FIG. 9(A), a reading device 100 has been disclosed which reads a hologram 104 recorded in a card 102. The reading device 100 is placed on the card 102 and the hologram 104 is irradiated with reference beam (e.g., see Japanese Patent Application Laid-Open Publication No. 2000-194794; hereinafter, “Patent Document 1”).
This reading device 100 is disposed with a light source 106 that emits reference beam. The reference beam is emitted from the light source 106 towards the hologram 104 and diffracted by the hologram 104, whereby a holographic image formed thereby is displayed on a screen 108 and read. The reading device 100 is disposed with a diffusion member 110 at a position where light reflected by the hologram 104 is made incident when the hologram 104 is in a readable position with respect to the reading device 100. By adjusting the position of the reading device 100 so that the diffusion member 110 becomes bright, the holographic image recorded on the card 102 is displayed on the screen 108.
However, in this reading device 100, an image optics (mirrors 112, 114 and 116) for separating the light reflected by the hologram 104 and the holographic image formed by the light being diffracted by the hologram 104 become necessary, which leads to an increase in the number of parts.
Thus, as shown in FIG. 9(B), Patent Document 1 also discloses a configuration where an abutment portion 118 that regulates the position of the hologram 104 is formed in a housing 120 of a reading device 130 at a position where the information of the hologram 104 is readable from the card 102, so that an end portion 102A of the card 102 abuts against the abutment portion 118 and the card 102 is positioned with respect to the reading device 130. However, it is necessary to dispose the hologram 104 in the card 102 at a position where the reference beam from the light source 106 is made incident when the end portion 102A of the card 102 abuts against the abutment portion 118. Namely, the region where the hologram 104 is formed (region where information is recorded) must be a determined position (same position from the end portion of the card 102) with respect to the abutment portion 118.
There is technology where an optical recording medium is formed, and various information is recorded in this optical recording medium with a hologram. As an example of the application of this technology, an optical recording medium is formed on paper printed with a printer, and information such as identification information and printing information is recorded in the optical recording medium by a hologram. A wide range of applications other than this is conceivable. Additionally, by using a reading device to read the information recorded by the hologram, the recorded information can be utilized.
However, in this case, the hologram is not limited to being formed always at a determined position with respect to the paper, and it is necessary to adjust the reading device to a readable position with respect to the hologram. As in Patent Document 1, when the hologram is formed at a constant determined position, the alignment between the reading device and the hologram can be easily adjusted by disposing an abutment portion such as shown in FIG. 9(B) in the reading device, but when the hologram is not formed at a determined position, it is difficult to align the position of the reading device with respect to the hologram. Also, the hologram can be reconstructed when reference beam is made incident from the same emission angle and emission direction as those at the time of recording, but when the hologram is formed on paper, there are instances where the angle at which the reference beam emitted from the light source of the reading device is made incident at the hologram does not match the condition for reconstructing the hologram due to the paper curling or to wrinkles, warps, rolls and rises in the paper, and in this case, the hologram is not reconstructed.